Conventionally, a demodulation circuit including a binarization circuit is provided in an in-vehicle system such as an RKE (Remote Keyless Entry) system. The binarization circuit is implemented by an analog circuit in which a comparator and a rapid charging-discharging circuit are combined. A capacitor that generates a reference voltage is connected to a reference terminal of the comparator. A resistor that fixes a threshold is connected to an external terminal of the rapid charging-discharging circuit.
Recently, it is demanded to shrink the binarization circuit. However, the shrinkage of the binarization circuit is limited because the binarization circuit is implemented by the analog circuit.